Ball release mechanism for measuring instruments



6 S 9 WMS 8 Rl Y oL E 3 TW N 3 mA R 5 vR .m 2 N. S I.| A m N s E M HV w @MH T J. s N I SR@ eww l Nm ums. wma M mw .Ne Jmm EF M E S A m m m MM 9^ 2., 1 G e D Patented Dec. 12, 1950 UNITED STATES PATENT OFFICE BALL RELEASE MECHANISM FOR MEASURING INSTRUMENTS Application November 26, 1948, Serial No. 62,095

Claims.

This invention relates to ball releasing or dropping mechanisms for determining the true horizontal or vertical position of an observation instrument, such as a sextant or the like, while making an observation.

Various types of ball dropping or releasing mechanisms have been extensively employed in sextants and other measuring instruments. One of the earlier forms of ball release mechanisms' included several retainers resembling the jaws of a chuck in which the ball was held preparatory to releasing it. The jaws were retracted to permit the ball to fall. With this type of mechanisms, the flight of the ball was erratic even when the release mechanism was not tilted, due to the fact that the ball had a tendency to roll olf one of the other of the jaws as it was being released.

An improved form of ball release mechanism was devised in which the ball is pressed upwardly by a spring against three points lying in a horizontal plane. In order to release the ball, the spring was swung downwardly out of the path of the ball with an acceleration greater than the acceleration due to gravity at the moment of release. This device suffers from the'disadvantage that up to the instant of release, the three locating points exert forces which have horizontal components. If these forces are not perfectly balanced or if they are Vnot released simultaneously, a horizontal component will appear in the iiight of the ball.

Other forms of ball release mechanisms including electromagnets having cup-shaped recesses therein for receiving the ball have also been devised but these ballrelease mechanisms, like the ones described above, are only really accurate when the magnet is disposed with its axis in a truly vertical position, as otherwise, the ball tends to be displaced off one edge or the other of the cup-shaped retaining recess, thereby imparting a horizontal component to its flight during fall.

An object of the present invention is to provide a means for releasing a spherical body, such as a steel ball, in space in such a manner as to relieve it of all horizontal components of force which would tend to throw the ball out of vertical ight.

Another object of the invention is to provide a ball release mechanism which reduces to a minimum the initial velocity of the ball in any direction for the purpose of permitting a truly vertical flight. Other objects of the invention will become apparent from the following description of a typical form of ball release mechanism embodying the present invention.

In accordance with the invention, a retaining and releasing mechanism is provided in which the ball is held under substantial pressure between two substantially parallel flat anvil members until the ball is ready for release.

In order to reduce the possibility of displacement of the ball by shock or vibration, a relatively large clamping force is necessary. However, such clamping force will produce a correspondingly great deformation of the ball and the clamping anvils so that should the lower anvil be suddenly removed, the elastic energy stored in the ball and in the upper anvil will impart to the ball an acceleration in a direction perpendicular to the face of the upper anvil. Inasmuch as the anvil face will not necessarily be horizontal due to a tilted position of the instrument, the ball would be thrown outwardly with a horizontal component in its ilight.

I'his objection is overcome, in the present invention, by removing the clamping force immediately prior to 'the release of the ball, but over a time interval suiiicient to allow the elastic energy of the ball and the upper anvil t0 be eX- pended, before the ball is released completely, The clamping force remaining is just sufficient `to overcome the weight of the ball; in other words, the clamping pressure at this instant is virtually zero. Release of the ball by moving the lower anvil away from itat an acceleration greater than the acceleration due to gravity will then permit the ball to fall freely from the face of the upper anvil with no horizontal component imparted to the ball even though the mechanism may be tilted substantially from the horizontal. In this way, the ball falls freely in a vertical line so that its point of impact will provide an accurate indication of true horizontal and vertical.

For a better understanding of the present in- `vention, reference may be had to the accompanying drawings, in which:

Fig. 1 is a perspective View of a schematic form of observation instrument such as an inclinometer and sextant illustrating the arrangement of the ball release mechanism thereon;

' Fig. 2 is a front view of the ball release mechanism rwith the casing therefor shown only partially and with the ball in tightly clamped position;

Fig. 3 is a front view of the release mechanism with the clamping pressure partially removedl 3 the device being shown partly in section and partly broken away; and

Fig. 4 is a front view of the mechanism partly in section and partly broken away illustrating the position of the parts at the moment of release of the ball.

The invention will be describedgenerally in relationto its application to an inclinometer `and sextant which is illustrated only schematically in the drawings for the reason that such devices are well-known and do not form a part oi the present invention. It will be understood that the ball release mechanism described hereinafter may be used with any typelof instrument requiring a ball release mechanism.

The inclinometer and sextant disclosed inFig. l includes a platform or base I,.from which extends vertically a limb Il upon whichthe sextant arm I2 and telescope I3 are mountedby means of a pivot Il. which is concentric with the arc |5 or r.ele-vationscale with .which .the-arm |2 7cooperates. Thelbase Ill-may be provided with a sheet of waxed riaperta-upon `which-a .mark-or dentis made `by the release of theball |1-.from.theballreleasemechanism i6.

4The ball release .Y mechanism I8, Yas illustrated, is. supported .by an arm .I9 which extendsr outwardly over the Ybase from the'upperend of the sextant limb I.

vIt will `be understood-that.theposition of the impression, dent or mark made by the vball on the .waxed paper -or other indicating medium indicates-the. inclination oi `the sextantwith re spect to -the horizontaland the vertical in the .usual way.

Itwillalsobeunderstood that the-waxed paper maybe advanced by means of` spools and-reels to yobtain.different readings and that other elements than waxed paper maybe used to indicate the point. of .impact of the ball. |1.

.litera-ming.now` to Fig-5.12, e land 4,1m@ balirelease mechanism embodying the present invention includes an -upper anvil member '.20 and a lowerfanvilmember'ZI ,between which thelball vfingers which engage -the periphery of theball 'and holdlit `until the anvil members' 2Iland' 2| arelbroug'ht up against the top and'bottom f the.` ball. ffterthe ball is grippedV by the anvil members, the fingers are withdrawn. Any. other type of ball-inserting means maybe'used finasmuchas such mechanism does not form .afpart of the present invention and many different types of such devices are known in the art.

-The lower anvil 2| is mounted onland extends upwardly from a rigid arm orAleverl 24 which yhas an upwardly extending armrotatably mounted on. a-.shaft 25 which extends `through theside walls .of the box orfhousing23. The shaft 25 also carries rotatably a plate'memberlZ having a forwardly projecting arm` 2l which overlies` the lever 24. rThe end of the arm 21 islprovided with asetscrew 28 which isV extended toward the lever 24 and limits the relative movement of the' lever 24 and the plate 26 in one direction. "The .lever 24 and the arm21 are urged toward each `other by. means of a light spring 29 `which is connected over the pins 35 and 36 on these levers, respectively, so that when the above described levers `and'y members are in the position shown in Fig. 2, the lower anvil 2| is urged against the ball I1 byatheforcesexerted by both of the springs 29 and 34.

`'lheflever 32.is maintained in an angular posivtion tensioning the spring 34, as shown in Fig. 2,

by means ofatrigger lever 31 which is pivotally mountedgon a plate 38 depending from the arm I9 on the sextant. Thep lever 31 is provided with a notched .end .portionj for .engaging a pin=40 in the upper., righthand corner .of fthe. member 32.130. retain' the" spring ,34 under tension.

`,TheA member 26' is l also vprovided with ,a notch 4| in its 'leading edge for. receiving` apin .'42 on the end of anotherretaining lever 43 `which is `also supported pivotally on .lthe l,plate 38. lThe levers 31 .and43.a're.crossed and `.they areconnected "by"mea'ns l of a coiljspring 43a tending to urge -them toward 'the [members 26 and -32, re- 'spectively The 'meinber's isffurther urgedtin` a. `counter- `clockwise `vdirect-ion by. vmeans of a heavy tension spring 144 -which isjconnectedto. the'pins 45. and

tively.

"In, order to 'release the trigger lever 31, .itais provided With a'latei'al 'extension "41 whichfis disposed lbelow .a plunger ,member ,48 ,sli'dably housing '23. The `j plunger. member is..` normally urged upwardly by irneansV tof "aspringie'a 'Theopera'tion ofthe mechanism ,will be u'nderstood vbest -`by reference bto "Fi-gs. "2, 3 fand 4 yof the""drawings. l "When the ball release mechanismis inthecondition shown in Eig.' 2, thellball.'y I ILisclamped..with heavy'pressure between the` anvils L'2 [l` and"2`| ,by .the forces -exerted bythe springSLZQanid'M. JThe meniber`26 is retainedl ina` "position to "stress the "springs 29 andifby means f"tli'e`stoplpnl`4`2 onthelever andV the' member 32.,.,1salso retained in a position to stress "thefspiingil @by means 'of the trigger lever 'Q31'and` the stop" pin Ljiljon 'the plate32. When the ball'is!tobereleasedlthe plunger 48 is" pushedv downwardly, `as "shown' in `FigfB, with the resultthatthe trigger'leVer`31 swings 'counterclockwise j :freeing it from Vthejpfin 40 y:and allowingthe'sp'ring'334i tomove" 'the'me'mberv 32in'a" C'Ou'nterclockwiseidirection, also rotatin'gthe shaft "25"andtheicrank`33. ,'As'the ineinber 32 rotates 'c'ountercl'o'ckwise uritierthe action ofitliespring 34,'the io'rce'exeited"bythasp in'g 34 decreasesto zero, at whichtime.,theball |"1 is held` in,A positiononlyiby" `the"'force1f .'theflight spring'Z 9'as shown in Fist.

As thememberBZ apprdaihesthelzero stress conditionfofthe s'pringf`34, Ialnlinclirie'd,cammng edge 49 on the member strikes theretaining or stoppin i2-and, rocks. this pin r.outof 'thenotch `4 I therebyl releasing theA member "2'6, rencounten clockwisefrotation by` meansof.l thel heavy. `spring 44. lAs the J :member "'25, rocks .counterclockwise relativeto the lever 24, the pressurewon theaba'll is, reduced to.u about zero.. attheitmethe.set-screw 28V strikes the lever 24. Due to the action of the heavy spring 44 on the lever 24, the impact of the set screw swings the latter -away from the ball with an acceleration greater than the acceleration due to gravity, as shown in Fig. 4, and continued movement of the member 34 and lever 2liA by the action of the spring @i4 moves the anvil 2l' completely out of the path of the ball I1.

The operation ofV the releasing mechanism,'

therefore, is, first, -to hold the ball Il with a heavy retaining pressure, as shown in Fig. 2, then, at the instant or" release, to relieve the ball fromy the heavy pressure, leaving only the light pressure exerted by the spring 29 to hold the ball lightly in position, followed'almost imnmediately by acomple'te release of pressure and movement of the lower supporting anvil 2l away from the ball to permit' the latter to fall vertically.

Inasmuch as the ball is not subjected to any appreciable pressure at the instant before its full release, elastic stresses are reduced to a minimum and the ball is not deflected horizontally. Thus the ball can fallin a true vertical line to give an accurate indication of the inclination of the instrument with respect to the horizontal and vertical. v

The ball release mechanism can be reset to receive another ball by means of the crank 33. When the crank 33 is rotated in a clockwise direction from the position shown in Fig. 4, the member 32 is likewise rotated clockwise toward the position in which the stop pin it engages in the notch 39 in the trigger lever 3l. As the member 32 is rotated toward the position shown in Fig. 2, its left-hand edge engages a fixed lug 5B on the member 26 and carries the member 25 also in a clockwise direction Yuntil the stop pin i2 drops in the notch 4I in the forward edge of the member 26. The pin 4G also engages in the notch 39 of the trigger lever 31, at about the same time as the pin 42 drops into the notch 4i, thereby resetting the entire mechanism `for another releasing operation.

It will be understood that the above-described release mechanism makes possible the exactly vertical release and fall of the ball Il even though the anvils Z and 2l are inclined substantially with respect to vertical or the face of the anvil may not be precisely horizontal.

It will be understood further that-the device may be modiiied in its details of construction, that the shape and size of the various elements may be modified as desired and that other releasing mechanisms than the plunger 48 and other resetting mechanisms than the crank 33 may be substituted, if desred. Therefore, the form of the invention described herein should be considered as illustrative and not as limiting the scope of the following claims.

I claim:

1. A ball release mechanism for determining the position of an instrument with respect to vertical and horizontal planes comprising an upper xed clamping member, a lower movable clamping member, rst means urging said lower clamping member toward said upper member to engage and clamp a ball between them with heavy retaining pressure, second means movable to relieve said ball of substantially all pressure, and third means responsive to movement of said second means to move said lower anvil member away from said ball with an acceleration greater than that due to gravity after said ball has been relieved of substantially all pressure.

2. A lball release mechanism for determining Gil the position of an instrument lwith respect toand away from said upper clamping member, iirst biasing means for urging said lower clamping member toward said upper clamping member with av strong force to engage and retain a ballbetween said clamping members, second biasing means to swing said lower clamping member away from said upper clamping member with an acceleration greater than that due to gravity, and means for actuating said irst and second biasing means, in succession, to reduce the biasing force of said first means almost to zero, and thereafter simultaneously render it completely vineffective and said second biasing means eiective.

3. A ball release mechanism for determining the position of an instrument with' respect to vertical and horizontal planes, comprising an upper xed clamping member, and a lower clamping member, said clamping members having plane surfaces to engage the top and bottom of a ball, means supporting said lower clamping member for swinging movement toward and away from said upper clamping member, first means for urging said lower clamping member toward said upper clamping member with light pressure, second means for moving said lower clamping member toward said upper clamping member with greater force, third means for swinging said lower clamping member away from said upper clamping member with an acceleration greater than that due to gravity, and means for actuating said first, second and third means to suc-4 said rockable member to said arm for exertingl a light stress on said arm urging said lower anvil member toward said upper anvil member in one position of said member, means on said rockable member engageable with said arm to move the lower anvil member out of alignment with said upper anvil member when said rockable member moves toward another position, means urging said rockable member toward said another position, means for releasably retaining said rockable member in said one position to clamp a ball lightly between said clamping surfaces, a movable member, means resiliently connecting the latter to said arm for exerting a more powerful stress on said arm to clamp said ball when the movable member is in one position and to relieve said stress when the movable member is in another position, means relea'sably retaining said movable member in said one position, and means for releasing successively said movable member and said rockable member for. movement toward their respective another posi` tions.

5. A ball release mechanism comprising a xed upper anvil member having a lower, substantially plane clamping surface, a pivoted arm adjacent to said upper anvil member, a lower anvil member extending upwardly from said arm and hav- 

